. >>> pope benedict xvi celebrated his last public mass as leader of the catholic church today. dressed in the traditional papal robes, the pope came had in on a wheeled platform. he presided over an ash wednesday mass at st. peter's basilica. the mass was moved to make room for the larger crowd that was expected after the pope announced that he's retiring on february 28. a conclave will start some time between march 15 and march 20. >> stopping the spread. still ahead, the unprecedented discovery in the bay area. >>> also, music meets nature. a story of a concert that is about to end. we'll have that coming up. >>> and i'm jeff ranieri in the weather center. a lot of sunshine today including some hazy conditions and expected air quality on moderate levels for thursday. if you have respiratory problems, maybe a tough day for you. we'll let you know when rain moves in and could clear this out. >>> a new sars-like virus is being reported. researchers expect it can spread from person to person. the virus causes severe respiratory illness, fever, and cough. so far only 11 cases have